The present invention is concerned with novel polyquinonic ionic compounds useful as electrode materials used for example in electrochemical generators.
Electrode materials derived from transition metals, in particular transition metals binary chalcogenides, such as TiS2, VOx (2xe2x89xa6xxe2x89xa62,5), ternary oxides such as LiNiO2 LiCoO2, Li1+xMn2xe2x88x92xO4(0xe2x89xa6xxe2x89xa61), et LiV3O8, are known. These materials are however often relatively toxic. With the exception of vanadium derivatives, the capacities are practically modest, i.e. on the order of 100 Ah.gxe2x88x921, and their potential (about 4 V vs Li+/Lio) are beyond the domain of stability of solid or liquid electrolytes. They are therefore problematic in terms of safety.
Organic compounds like conjugated polymers work through an insertion mechanism of anions taken from the electrolyte. The mass capacities resulting therefrom are consequently low and the cycling possibilities are disappointing.
Other known compounds are those of the polydisulfide type, which, even if they do not have intrinsic electronic conductivity, possess interesting redox properties and mass capacities ((xe2x89xa7300 Ah.gxe2x88x921), particularly oxidizing coupling derivatives of 2,5-dimercaptothiadiazole. However, the resulting reduction products and intermediates are lithium salts like conjugated thiolates with a nitrogen atom. Delocalization of the charge on the polarisable anionic centers like sulfur and nitrogen, lead to a relatively important solubility in the electrolytes, as well as a reduced cycling life span.
Monoquinones are organic compounds known for their redox properties, but the potentials are of little interest (on the order of 2.2 V vs. Li+/Lio), and the neutral oxidized compounds are soluble in the electrolytes. Polymers bearing quinonic functions such as those resulting from hydroquinone and formaldehyde polycondensation, are not electrochemically active because of the reduced mobility of the charge carriers, ions and electrons, in the absence of highly polar protic solvents like water.
The present invention concerns electroactive compounds derived from anion salts bearing at least 2 quinone functions cumulated, conjugated, or both, in the same molecule. More specifically, the invention comprises a redox compound having at least one state of oxidation state represented by the general formula: 
wherein
M+ represents an alkaline metallic cation, an alkaline-earth cation, a transition metal cation, a rare earth cation, an organometallic cation, an organic cation of the xe2x80x9cniumxe2x80x9d type, a repetitive unit of a cationic oxidized conjugated polymer, or a monomeric or polymeric cation optionally having a redox character;
X is oxygen, NCN, or C(CN)2;
Z is Cxe2x80x94Yxe2x88x92 or Nxe2x88x92;
Y represents oxygen, sulfur, NCN, xe2x80x94C(CN)2, with the proviso that when Y is sulfur and n is xe2x89xa64, then X is oxygen;
R1 is absent, O, S, NH, xe2x80x94(Cxe2x95x90C)rxe2x80x94, xe2x80x94(Wxe2x95x90W)rxe2x80x94 wherein W is independently CR6 or N; r varies between 1 and 12; and R6 is H, halogen, CN, or C1-12 alkyl, C2-12 alkenyl or C6-14 aryl optionally having one or more substituents oxa, aza or thia; and wherein 2 R6 groups can be bonded to form a cycle comprising from 3 to 7 members;
R2 and R3 are the same or different and are absent, a carbonated divalent radical, optionally substituted with aza, oxa or thia;
q varies between 0 et p;
p varies between 1 and 5;
n varies between 1 and 104; and
wherein two of R1, R2 and R3 can be bonded together to form a cycle comprising 3 to 7 members.
For the purposes of the present invention, when n is 4 or less, the compound of the invention is not considered a polymer. In addition, the expression xe2x80x9cdivalent radicalxe2x80x9d is defined as an alkylene, an arylene, or an arylalkylene of from 2 to 200 carbon atoms, and optionally comprising one or more substituents aza, oxa or thia.
The present application further concerns an electrode material characterized in that it contains, in whole or in part, a compound of the invention, and an electrical energy storage system such as a primary or secondary generator or a super capacity comprising an electrolyte, at least one negative electrode and at least one positive electrode comprising a compound of the invention.
In the present invention, a new family of electroactive compounds derived from anion salts bearing a plurality of quinone functions cumulated and/or conjugated in the same molecule is described and claimed. It has been found that such type of compounds have a high capacity, i.e. equal or higher than 300 Ah.gxe2x88x921, obtained at potentials comprised between 3.5 et 1 V vs. Li+/Lio, thus in the domain of stability of conventional aprotic electrolytes, liquid or solid, and allowing the making of positive and negative electrodes for generators. Further, the corresponding salts do not, whatever their degree of oxidation, solubilize significantly in liquid electrolytes or aprotic polymers. The kinetic of theredox reaction in solid phase is noticeable and comparable to that of inorganic insertion materials. It has also been found that by replacing the oxygen atom of the neutral quinonic groups CO with NCN groups or C(CN)2, and/or the replacement of the oxygen atom of the quinonic groups negatively charged with anionic groups Nxe2x88x92, NCNxe2x88x92 or C(CN)2xe2x88x92 had the same interesting properties in terms of the redox activity. The redox potential is displaced of about 300 mV towards the positive values by replacing a neutral quinonic oxygen with an NCN or C(CN)2. The chemical methods to perform these substitutions on the quinonic groups are well known to anyone of ordinary skill in the art.
The redox compounds of the present invention include also polyquinones wherein the negatively charged oxygen of the quinonic groups is replaced with sulfur Sxe2x88x92. In this case, charge conjugation with an oxygenated group CO neutral and weakly polarisable and more electronegative, significantly lowers the solubility of the corresponding ionic derivatives, in particular in electrolytic solutions. An additional degree of oxidation is then obtained by oxidative duplication of CSxe2x88x92 groups to form disulfide bridges CSxe2x80x94SC.
These polyquinonic compounds can also be part of the polymers into which the charges are conjugated along the polymeric chain. In such a case, the solubility of these rigid macromolecules is null, whatever the charge borne by the polymer, thus including the neutral state.
Because the compounds of the present invention are anion salts, i.e., negatively charged, it is necessary to combine them with a cation in order to have a global neutral charge. The preferred cations comprise the proton, alkaline cations like Li, Na, K, Cs; alkaline-earth cations like Mg, Ca, Ba; transition metal cations like Cu, Zn, Pb, Fe, Ni, Co, Mn, V, Cr; rare earth cations; organometallic cations like metallocenium; cations of the  less than  less than ium greater than  greater than  type such as ammonium, amidinium, guanidinium, pyridinium, imidazolium, triazolium, imidazolinium, sulfonium, phosphonium, iodinium; a repetitive unit of an oxidized cationic conjugated polymer such as polypyrrole, polythiophene, polyquinolines; cations in the form of monomers or polymers optionally having a redox character such as viologenes of formula [xe2x80x94(Rxe2x80x3NC5H4xe2x80x94C5H4Nxe2x80x94)2+]n wherein Rxe2x80x3 comprises C2-12 alkylene, C6-14 arylene or C6-14 arylene C2-12 alkylene, each optionally substituted with oxa, aza ou thia. The lithium cation and the proton are particularly preferred. Other ions can be present in the electrolytic medium and/or in the electrode material, and can contribute to improve the conductivity of the interfacial properties. The potassium ion is advantageously used in such instance, as well as cations derived from quatemized imidazoliumn.
To the redox capacity of the molecules of the present invention can be added that of the cation when the latter possesses many degrees of oxidation. Cations of iron, copper or manganese, as well as metallocenes, are particularly interesting for such application. Organic cations with redox properties, such as viologenes, are similarly useful. These cations can optionally be part of a polymeric chain.
The compounds of the present invention possess high specific capacities of redox exchange, and in fact superior to those of conventional inorganic compounds. The great variety of functional groups available allows choosing redox potentials in a wide range of potentials, typically between 0.1 to 3.7 V vs. Li+/Lio. Compounds with redox couples comprised between 0.1 and 2 V vs. Li+/Lio are advantageously used as a component of negative electrodes in electrochemical generators of primary and secondary type batteries or supercapacitor. Similarly, compounds with redox couples comprised between 2 and 3.7 V vs. Li+/Lio are advantageously used as component of positive electrodes in same devices or as an active or passive electrode in electrochromic devices.
The compounds of the present invention can be used alone or in mixtures thereof They can also be used in conjunction with other redox compounds, in particular insertion compounds. Such insertion compounds include, for negative electrodes, metallic lithium or alloys thereof, optionally in the form of a nanometric dispersion in lithium oxide; double nitrides of lithium and a metal of transition such as cobalt; oxides with a low potential of general formula Li1+yTi2xe2x88x92x/4O4 wherein x and y vary between 0 et 1; and carbon and carbonated products resulting from the pyrolysis of organic matters. For the positive electrodes, the insertion compounds include oxides and sulfides of transition metals, such as VOz wherein z varies between 2 and 2.5; LiV3O8; LiaN1xe2x88x92aCoaO2 wherein a varies between 0 et 1; manganese spinels LiyMn2xe2x88x92xMxO4 wherein x varies between 0 and 0.5 and y varies between 0 and 2, and M is Li, Cr, Al, V, Ni; organic polydisulfides; FeS; FeS2; iron sulfate; iron and lithium phosphates and phosphosilicates of the olivine structure; or the substitution product of iron with manganese, either used alone or in mixtures.
The materials of the invention are particularly embodied in composite electrodes containing the novel redox compounds, alone or in mixtures, at least one electronic conductor, and at least one polymeric binder. The electronic conductors are preferably selected from carbonated compounds such as carbon black, graphite powder, products resulting from the pyrolysis of organic matters, in particular phenolic resins or polyacrylonitrile. When the electrode binder does not have any electrochemical function but only a mechanical function, the latter is advantageously chosen from non-polar polymers like polytetrafluoroethylene, co- or ter-polymer of ethylene, propylene and a diene, that allow the binding of the materials while leaving a porosity sufficient to permit the required electrolyte penetration for proper operation of these redox materials.
Liquid electrolytes suitable with such type of redox materials are those obtained by dissolving a salt or an acid in a solvent. The solvents are preferably chosen from cyclic or acyclic carbonates, xcex3-butyrolactone, monoalkylamides and di-alkylamides, tetraalkylsulfamides, dialkylated ethers of mono, di, tri and tetraethylene glycols, as well as oligomers having a mass lower than 2000 g/mole, and their mixtures.
In a variation, the electrode binder has an ionic conductivity and allows the maintenance of an intimate contact between the particles of the redox materials in the electrolyte while compensating, because of their plastic or elastomeric character, for the variations of volume inherent to the operation of the electrode. In preferred embodiments, the electrolyte contains, individually or in a mixture, a polar-type polymer, a polar solvent, and/or at least one ionic salt. The polar-type polymers useful with the addition of a liquid solvent are preferably selected from vinylidene fluoride-based homo- or copolymers, acrylonitrile-based homo- or copolymers, methyl methacrylate-based homo- or copolymers. The polar-type polymers useful with or without the addition of a liquid solvent are preferably selected from polyethers such as ethylene oxide-based or propylene oxide-based homo- or copolymers. In a variation of the preferred embodiment of the compounds of the invention, ceramic or cross-linked particles are added to the polymer electrolytes, to improve the mechanical properties.
Another interesting aspect of certain compounds of the invention is their possibility to give, after oxidation beyond the normal reversible operating potential, an irreversible reaction liberating lithium ions and gaseous compounds such as carbon monoxide or carbon dioxide, nitrogen, ethylene or acetylene and their polymers. These products are eliminated from the generator medium (gas) or are inactive (polymers), and provide exceeding capacity that is useful to compensate for the loss of capacity equilibrium between the anode and the cathode, caused mainly by the appearance of a passivation layer during the first operating cycles of the generator.
The following anions are illustrate compounds of the present invention, and should not be considered as limiting its scope. 
The following examples are provided to illustrate preferred embodiments of the present invention, and should not be considered as limiting its scope.